Green’s Dictionary of Slang

brick v.⁵

to be terrified; usu. as brick oneself.

1996		P. Howard The Joy (2015) [ebook] He must have been bricking himself all night, because he had that look about him the next morning, as though he’d had no sleep.
2001		OnLine Dict. of Playground Sl. 🌐 brick v. to shit oneself in fear especially when hard lads are chasing you down the alley: brickin’ yourself.

In phrases

brick it (v.)

to be terrified, to be very nervous.

1998		M. Newall ‘Sir Gawayne and the Grene Knight’ in Indep. Weekend Rev. 26 Dec. 1: Bye nowe he’s brickyng it.
1999		K. Sampson Powder 130: Next morning everyone’s bricking it.
2005		P. Howard Curious Incident of the Dog in the Nightdress 153: I am seriously bricking it.
2013		K. Sampson Killing Pool 304: I hunch my shoulders and feel for the pistol, bricking it all of a sudden.
2015		L. McInerney Glorious Heresies 153: ‘I was bricking it. I thought he was going to kill me’.
2021		Twitter 7 Dec. 🌐 The only thing that gives me slight pleasure is the thought of [Brois] Johnson bricking it re how to deal with this, and the roasting he’ll get at PMQs.
2021		P Howard Braywatch 282: ‘They’re bricking it [...] Should we go out hard in the second half and finish them off, like?’.